This invention relates generally to switching apparatus and more particularly to a disconnect switch and ground strip therefor particularly adapted for use with gas insulated power systems.
In recent years, there has come about a demand for a reduced-size substation. This demand on the part of public utilities has been met by gas insulated substation equipment. This type of substation equipment significantly reduces the space required by the high voltage value of substations rated, for example, 46 Kv through 500 Kv. Space reduction is accomplished by replacing the open-bus and the air-tight bushings with gas insulated bus filled, for example, with a highly insulating gas such as sulfur hexafluoride gas at a pressure, for example, of 45 pounds per square inch gauge and thereby permitting the movement of electrical equipment very closely together.
This gas insulated substation equipment has many advantages, among which are: significant reduction in size requirements both in land area and overall height; added system reliability by eliminating the possibility of phase-to-phase fault, lighting strikes within the system, or contamination of insulators; reduced maintenance because the closed system is isolated from the environment; added personnel safety because all live parts are covered by ground shields; and lower installation costs as compared with conventional or other types of power systems when the gas insulated modular approach is utilized.
The gas insulating system, as briefly described above, has additional design strategies, inasmuch as the high voltage equipment is compressed, so that both the space required and the total length is minimized. The power transformers may be located on outside corners so as to be capable of ready removal, and the location of cable pot heads is flexible, with results that the system may be readily connected to overhead transmission lines.
It is desirable to provide a disconnect switch which will permit the isolation of certain sections of the gas insulator system regarding such a scheme, reference can be had, for example to U.S. Pat. Nos. 4,107,498--Disconnect Switch and Drive Mechanism Therefor, issued Aug. 15, 1978 to Golota, assigned to the assignee of the present invention; 3,987,260--Ground and Test Connection for SF.sub.6 Insulated Bus, issued Oct. 19, 1976 to Wilson; 3,876,846--Combination Ground and Test Switch Apparatus for Pressurized-Gas-Insulated High Voltage Systems, issued Apr. 8, 1975 to Graybill; 3,610,858--Disconnect Device for Fully Insulated High-Voltage Electrical Switch Gear With Individually Reciprocal Contacts, issued Oct. 5, 1971 to Mannheim et al. The named patents teach different methods of engaging or disengaging contacts or the grounding of contacts for isolation and test purposes which are required by electrical standards.
It would be advantageous however, to provide a means which is less complex and less expensive to produce. It would also be desirable to provide a grounding means so that upon the opening of the switch, a portion of the high voltage system can be both electrically isolated and electrically neutralized thereby providing a safe working condition.